During the upload a temporary file is going to be used, but you have access to file when the upload is done.
Check the sample for the file size, inside the action FileUpload_GetResult. You can execute any logic there, including to store this file inside your database entity.

Would be really great to see some prescriptive example of doing mentioned (i.e diagram on how to save selected file to db entity using the extension)!
P.S still not getting where do I catch the name/location of the uploaded file
Thanks